The present invention relates to a measuring circuit and more particularly to a circuit for establishing the average value of a selected number of input values.
In industry and commerce, the weights of objects or materials must often be accurately ascertained. As one example, the exact weight of letters or parcels to be mailed in the national postal system must be ascertained so that the user will know how much postage he is required to use. If the weight cannot be accurately measured, the user may place too little or too much postage on the mailed item. If not enough postage is used, the postal service will normally return the item to the mailer resulting in delayed delivery. If too much postage is used, the mailer is wasting money. While the cost of excess postage may be low on a per item basis, the accumulated costs over a period of time can be very significant.
A number of known scale mechanisms are capable of consistently measuring weight with the requisite accuracy when the mechanisms are used under ideal operating conditions. However, scales employed in industry and commerce are rarely used under ideal conditions. For example, such scales are normally located in buildings which also contain electromechanical machinery, such as compressors, generators, air conditioners, etc. Such machines, many of which are firmly anchored to the floor or (in the case of air conditioners) to the roof of the building vibrate at a relatively low frequency during operation. As a result, vibrations are set up in the floor and walls of the building. These vibrations can be transmitted to the scale mechanisms to cause "jitter" in the scale output making it difficult to obtain an accurate reading.
In certain relatively sophisticated systems, the scale output may be applied directly to a computerized control unit which utilizes the weight-representing signal in further computations; for example, the calculation of postage required for a letter or parcel. Where the weight-representing signals are applied directly to a control unit, there is no opportunity for an operator to decide whether visually-detected "jitter" in the scale output is too great to prevent an accurate scale reading. In such systems, it becomes even more critical that an accurate scale reading be obtained.